1. Field of the Invention
The present invention is related to copy protection. In particular, the present invention is related to copy protection using scrambling keys.
2. Description of Related Art
Copy protection management provides mechanisms to prevent unauthorized copying of clear content. In a typical scenario, a content provider supplies a content to a user via a medium. The medium may be a communication medium such as air, a communication network, or a hardware device, e.g. DVD disk, embodying the content. The content is scrambled by the content provider in a certain way. The scrambled content is then delivered the user's reader or viewing device. The user's reader or viewing device unscrambles the scrambled digital content and provides the content in the clear for viewing reading, or listening. The clear digital content would typically have copy protection applied to it such as Digital Transmission Copy Protection (DTCP) or watermarking. The copy protection, for example, could limit copying of the clear content to “Copy Never” or “Copy Once”.
Conditional access (CA) devices are those user's viewing, reading, or listening devices that provide conditional access to the content. Entitlement management messages (EMM) typically use unique keys or signatures to deliver privileges (e.g., rights, keys) to a particular CA device. Typically, in broadcast systems, a group entitlement right of group key would be delivered to the CA device. Typically the group are users or customers who share a particular set of entitlements, e.g. HBO or Disney.
Current copy protection schemes allow the copying of CA scrambled content as “Copy Free”. Yet the CA unscrambled content may or may not be copiable based on the Copy Protection status of the content. A content provider may choose to mark certain types of CA unscrambled content as “Copy Never” where there can never be copying of the CA unscrambled content. In such an approach, the content stored and kept in CA scrambled format. There are a number of problems with such a copy protection approach.
First, if the content is locally scrambled with a unique CA key or unique access right in a particular CA device, then it is difficult to play back the content in another CA device located elsewhere. As an example, in a home environment, if a set-top box has a unique CA key or access right to de-scramble the content delivered by a cable service provider, then only that particular set-top box can provide access to the content. Other set-top boxes located elsewhere (e.g., other rooms, or in the car, or portable devices like a Walkman) cannot access the content.
Second, if the CA device with a unique CA key or unique access right fails to work for any reason, then the content stored with, or received by, that device may not be retrievable. A user's entire archive of movies, music, and other content stored with that unique CA key or unique access right of a particular CA device nay be lost. These and other problems create inconveniences and frustrations for the user, and may also limit the services provided by the content provider.
Therefore, there is a need for a more flexible for handling copy protected content to accommodate multiple access devices.